Remote control devices for operating various forms of equipment in response to transmitted signals go back many years (U.S. Pat. No. 1,844,177 (radios, lamps); U.S. Pat. No. 2,396,699, underwater mines; U.S. Pat. No. 2,433,845, relays; U.S. Pat. No. 3,829,683--computerized). Use of such equipments by disabled persons has likewise been suggested in the prior art (U.S. Pat. No. 3,286,031). A particularly relevant device for use by disabled persons was developed in the early 1970's at Bell Labs (see Bell Labs Record, Vol. 51, No. 7, Oct. 1973), by which the operator is able to dial a telephone or to operate one or two appliances by the mere creation of a noise at an appropriate time. The Bell Labs device employs a clock-like dial face equipped to illuminate the digits in timed sequence. The device is commanded by making a loud noise while a given light is illuminated, and reception of the signal at that instant causes the device to respond correspondingly to the number then illuminated. Thus, making the noise in coincidence with the illumination of a given number, or a given sequence of numbers provides a command. In one example, the device is described as using the sequence of sounds coincident with the illumination of numbers 3, 6, and 9 to initiate a telephone dialing sequence. After receipt of the initiating command, a red light adjacent to the dial face is illuminated and indicates to the operator that the device is ready to receive dialing instructions. Thereafter, the operator makes a loud noise as each of the numbers he wishes to dial becomes illuminated in sequence. A light in the center of the dial flashes momentarily to inform him that each number commanded has been received. When the completed telephone number has been fully entered, the operator waits until letter "D" on the dial face becomes illuminated, he then makes a loud noise, and again a second loud noise as the illumination proceeds to the next digit. This sequence causes an automatic dialer to take over and make the telephone call. Hanging up the telephone and various other functions are performed in response to commands given and processed in a similar way.
The Bell Labs device, however, has a number of serious drawbacks which have prevented its adoption. The major problem has to do with reception of false commands. In order for the Bell Labs device to work properly, the environment must be virtually free of random noise, because otherwise a false command will be entered, forcing the operator to erase what he has done and start over at the beginning of the command sequence. In other cases, a false entry coming from ambient noise or noise in a radio program can cause the interruption of the program. The Bell Labs device uses a coded initiating command procedure (e.g. the sequence of 3, 6, 9) to minimize the risks of false interruption, but this, in itself, is a drawback because of the extra time required to make the coded initiating entry.
Accordingly, a basic object of the present invention is to provide a remote control device which is extremely simple to control and which is virtually immune to false triggering and unintentional interruption of service. More detailed objectives are to provide a sound operated remote control which can operate in a normal sound environment including the sound of radio, television or taped programs--or normal voice transmissions, and accomplish this without the use of time consuming coding procedures. Another object is to provide a device in which commands for a multiplicity of functions can be accomplished using a single command without time consuming coding procedures.